1. Field of the Invention
This invention relates generally to the art of detecting leaks in fluid flow systems, and more particularly to a double tracer gas process for detecting leakages in underground conduit type piping systems.
2. Description of the Prior Art
It is known in the art of detecting leaks in fluid flow systems to employ a tracer gas for detecting leakages in underground conduit type piping systems. Steam, high temperature hot water, chilled water, hot oil and other products are frequently piped through underground conduit type piping syetems. These systems comprise a carrier pipe which is surrounded by a protective conduit. Insulating material may be disposed around the carrier pipe and inside of the protective conduit. The protective conduit also provides an insulating space between the carrier pipe and the surrounding earth. Any failure of the protective conduit which allows ground water to enter the protective conduit destroys the insulating qualities of the piping system and creates a corrosive atmosphere in the protective conduit which could lead to failure of the carrier pipe. Accordingly, periodic pressure tests of the protective conduit are desirable to determine the presence of leaks. If the leaks are detected by a drop in pressure, a means of pinpointing these leaks is necessary.
Heretofore, leaks in the aforementioned protective conduits were detected by introducing materials such as peppermint or mercaptan with high odor levels into the protective conduit. This practice resulted in the detection of only very large leaks. Heretofore, various single tracer gases were also used, such as helium or Freon, and some success has been achieved with such tracer gases. However, interfering gases in the soil, such as carbon dioxide, have resulted in confusion and missed leaks when single tracer gases such as helium or Freon are employed. Examples of prior art patents showing the use of prior art tracer gases are U.S. Pat. Nos. 2,486,199, 2,928,247, 2,996,661, 3,036,457, 3,085,423, and 3,106,089.